The present invention relates to a muffler, and more particularly, to a muffler of the expansion type for use with an engine of an automobile and the like.
Heretofore a muffler of the expansion type has been used for muffling the sound of the exhaust gas of the engine, the pressure of which varies in pulsating manner, wherein the exhaust gas is first expanded and then contracted in traversing the muffler.
However, such a prior art muffler of the expansion type has the disadvantage that extraneous noise will be emitted from the outlet pipe rapid acceleration or rapid deceleration of the engine, although the muffler may be effective under normal driving conditions. Further, the muffler may generate extraneous noise depending upon the position thereof with respect to the engine, even though the above mentioned disadvantage is avoided.
In the prior art muffler of the expansion type, when the exhaust gas introducing pipe is formed, many working steps are required, such steps including pipe diameter throttling, welding and the like, so that manufacture of the exhaust gas introducing pipe or muffler becomes troublesome. Also, during operation of the muffler, damage to the exhaust gas introducing pipe is cuased as the result of working stress therein, the heat of the exhaust gas and the like leading to failure of the muffling effect and the life of the muffler will become short.
Further, in the prior art muffler of the expansion type, the securing of the exhaust gas conducting pipes to the main body of the muffler could not be made rigid, so that the pipes tended to detach from the mating recesses or the mating cylindrical flanges of the main body of the muffler. Also, when the pipes were secured to mating portions by welding, the welding operation was very troublesome, so that the welded portions suffered from being broken or the pipes might be jolted or separate from the mating portions due to severe vibration of the main body of the muffler, the thermal expansion of the main body resulting from the passage of high temperature exhaust gas through the muffler or the failure of the welded portions in the fixing construction of the pipes.